Method for selecting the composition of a construction material comprising an excavated clay soil, method and system for preparing such a construction material

ABSTRACT

The invention relates to a method ( 100 ) for selecting the composition of a construction material including an excavated clay soil, said construction material composition to include deflocculating agent and activating agent quantities adapted to the excavated clay soil, said method including a step of receiving ( 130 ) a measured value of at least one physicochemical property of an excavated clay soil, and a step of selecting ( 170 ) a deflocculating agent quantity and an activating agent quantity adapted to the excavated clay soil. In addition, the invention also relates to a method ( 200 ) for calibrating a calculation algorithm for determining the composition of a site construction material, to a construction material formed from an excavated clay soil, and to a system ( 400 ) for preparing a construction material including an excavated clay soil.

This application is a continuation of U.S. Pat. No. 11,401,215 filedSep. 7, 2021, which is the US national stage of PCT/FR2020/050469 filedMar. 6, 2020, the contents of which are incorporated by reference.

The invention relates to the field of construction materials, and moreparticularly that of materials which can be used in construction such asconstruction binders or concretes. The invention relates to a method forselecting the composition of a construction material including anexcavated clay soil. The invention also relates to a method forcalibrating a calculation algorithm for determining the composition of asite construction material including excavated clay soil, to aconstruction material formed from an excavated clay soil, and to asystem for preparing a construction material including an excavated claysoil.

PRIOR ART

Cement is the second most consumed resource in the world, with more than4 billion tons of material produced each year worldwide, and thisconsumption is constantly increasing, driven by the growing demand forhousing and infrastructure.

Cement is a binder, usually hydraulic, which when mixed with waterhardens and sets. After curing, the cement retains its strength andstability even when exposed to water. There is a wide variety of cementsused around the world. In addition, cement preparation methods arebecoming increasingly sophisticated and automated systems for thepreparation of various types of concrete have been developed (FR2751911,EP2296854).

Nevertheless, all conventional cements contain clinker at a percentagevarying from 5% for some blast furnace cements to a minimum of 95% forPortland cement, which is the most widely used cement in the worldtoday. Clinker is the result of firing a mixture comprised of about 80%limestone and 20% aluminosilicates (such as clays). This firing,clinkerization, is done at a temperature of more than 1200° C.,therefore such a cement preparation method implies a high energyconsumption. In addition, the chemical conversion of limestone to limealso releases carbon dioxide. As a result, the cement industry generatesabout 8% of global CO₂ emissions. In response to this challenge,industry and researchers are exploring ways to reduce the impact ofcarbon dioxide emissions from the cement industry.

In addition to these carbon emissions, the management of excavated soilis also an issue in the context of large urban development projects.This excavated soil is generally stored or used to fill in quarries, orfor park development, but the potential use is much lower than thevolumes available. In addition, it has been proposed to use thisexcavated earth for the production of construction materials, but thisapplication comes up against the problems of insufficient mechanicalstrength of raw soil constructions, on the one hand, and the non-optimalcarbon footprint when using metakaolin.

Indeed, the proposed cements based on raw earth, as described indocument FR3016376, either have physical properties, such as improvedmechanical strength, reduced capillary absorption, or reducedpermeability to liquids, which are too weak; or they require theaddition of a portion of Portland cement in order to have acceptablemechanical properties.

For metakaolin-based cements, the mixture of lime or sodium hydroxideand metakaolin during the hydration of the cement will induce apozzolanic reaction. This reaction improves the binding properties ofmetakaolin cements. Because of these properties, metakaolin-basedconstruction materials have been proposed, including in particular aflashed metakaolin associated with sodium hydroxide, as described indocument FR3034094. Nevertheless, the formation of metakaolin requires athermal treatment of kaolinitic clays to lead to the dehydroxylation ofthe kaolinite crystalline structure, which induces an unfavorable carbonbalance, especially when taking into account the transport of excavatedsoil to the thermal units.

Thus, there is a need for new uses of excavated clay soil that canadvantageously allow for a reduction of greenhouse gas emissions and thepreparation of a construction material such as a construction binder ora site concrete with a low carbon footprint while having mechanicalproperties at least equivalent or even superior to the mechanicalproperties of cements commonly used in the construction industry.

Technical Problem

The invention therefore aims to overcome the disadvantages of the priorart. In particular, the invention aims to provide a method for selectingthe composition of a construction material including an excavated claysoil, said method making it possible to form a construction material,such as a construction binder, for reducing, on the one hand, theemission of greenhouse gases, such as carbon dioxide, while at the sametime conferring mechanical characteristics suitable for its use in theconstruction industry, and, on the other hand, to propose a siteconcrete including such a binder and capable of improving the comfort ofthe inhabitants in comparison with a concrete formed from Portlandcement.

The invention also aims to propose a construction material formed froman excavated clay soil with mechanical properties suitable for its usein the construction industry, while constituting a way of reclaimingexcavated clay soil.

The invention also aims to propose a method and a system for preparing aconstruction material including an excavated clay soil for reducing theemission of greenhouse gases compared to a conventional constructionmaterial of the Portland cement type.

BRIEF DESCRIPTION OF THE INVENTION

To this end, the invention relates to a method for selecting thecomposition of a construction material including an excavated clay soil,said construction material composition to include deflocculating agentand activating agent quantities adapted to the excavated clay soil, saidmethod being implemented by a computer device including a calculationmodule, said method including:

-   -   A step of receiving, from the calculation module, a measured        value of at least one physicochemical property of an excavated        clay soil; and    -   A step of selecting, by the calculation module, a deflocculating        agent quantity and an activating agent quantity adapted to the        excavated clay soil based on a comparison of the one or more        measured values with reference values, said reference values        including correlations between measured values of at least one        physicochemical property of a clay soil and deflocculating agent        and activating agent quantities adapted to said clay soil to        form a construction material.

Such a selection method has the advantage of being able to select atleast part of the constituents of a construction material based on anexcavated clay soil so as to form a construction material, such as aconstruction binder or a site concrete, with mechanical propertiesequivalent to the mechanical properties of conventional constructionmaterials using clinkers. Indeed, with the methods of the prior art, theconstruction materials obtained from excavated soil are generally notsufficiently efficient from a mechanical point of view to allow for awide use.

Furthermore, the constituents selected by the selection method (i.e.excavated clay soil, deflocculating agent, and activating agent) allowthe formation of a construction material in a less energy consumingpreparation method.

Finally, since the construction material includes an excavated claysoil, preferably not having undergone a combustion stage, itadvantageous retains hygrothermal properties allowing the comfort of theinhabitants to be improved compared with a concrete formed from Portlandcement.

According to other optional features of the selection method:

-   -   the at least one physicochemical property is selected from: the        content of clays in the excavated clay soil, the nature of the        clays, the particle size, the content of impurities, the content        of non-clay mineralogical fractions, the content of        contaminants, the elemental analysis, the content of metal        oxides, the salinity, the pH, and the total exchange capacity of        the clay in the excavated clay soil. Preferably, the at least        one physicochemical property is selected from: the content of        clays in the excavated clay soil, the nature of the clays, the        particle size, the content of non-clay mineralogical fractions,        the elemental analysis, the content of metal oxides, the        salinity, the pH, and the total exchange capacity of the clay in        the excavated clay soil. More preferably, the at least one        physicochemical property is selected from: the content of clays        in the excavated clay soil, the nature of the clays, the        particle size, the content of non-clay mineralogical fractions,        the content of metal oxides, and the total exchange capacity of        the clay in the excavated clay soil. Such physicochemical        properties are the most likely to provide deflocculating agent        and activating agent values adapted to the excavated clay soil        considered.    -   the at least one physicochemical property is measured on a        pretreated excavated clay soil, said pretreatment being selected        from: crushing, sorting, sieving, and/or drying of the excavated        clay soil. This advantageously allows the error in the        measurements made to be minimized. Preferably, the pretreatment        includes at least one fractionation, for example by sieving or        sedimentation, more preferably fractionation at 50 μm and for        example fractionation at 20 μm.    -   It previously comprises receiving a desired mechanical property        value of the construction material and the step of selecting the        deflocculating agent and activating agent quantities further        includes excluding the deflocculating agent and activating agent        quantities which will not allow the construction material to        exhibit the desired mechanical property value. Thus, an operator        can easily set an objective performance criterion for the        construction material, the composition of which is expected.        This saves time and performance is increased in the process of        reclaiming excavated soil for a construction application.    -   the step of selecting, by the calculation module, a        deflocculating agent quantity and an activating agent quantity        adapted to the excavated clay soil includes implementing a        previously calibrated calculation algorithm.    -   the previously calibrated calculation algorithm has been        obtained by implementing a statistical supervised learning        method.

According to another aspect, the invention further relates to a methodfor calibrating a calculation algorithm for determining the compositionof a construction material, such as a construction binder or a siteconcrete, for example implemented by a digital device including alearning module, characterized in that it includes:

-   -   A first step of receiving, from the learning module, a measured        value of at least one physicochemical property of an excavated        clay soil;    -   A second step of receiving, from the learning module, a        deflocculating agent quantity value and an activating agent        quantity value which, when added to the excavated clay soil,        allow a construction material to be formed;    -   A third step of receiving, from the learning module, a measured        value of at least one mechanical property of the construction        material formed from the excavated clay soil, the value of at        least one physicochemical property of which was received in the        first receiving step, and from the deflocculating agent and        activating agent quantities received in the second reception        step; and    -   A step of creating a correlation, by the learning module,        between the received measured values in order to calibrate a        calculation algorithm.

The combination of an excavated clay soil, a deflocculating agent, andan activating agent allows a construction material with appreciablemechanical properties to be produced and the selection method accordingto the invention allows appropriate quantity values to be selected.However, considering the complexity and variability of thephysicochemical properties of the excavated clay soils, the inventorshave developed a method of calibrating a calculation algorithm allowingthis complexity to be overcome. Such a calibration method allowsdeflocculating agent and activating agent quantity values to be proposedthat are highly adapted to the excavated clay soil. It should be notedthat the reception order is not important and allows the description ofthe method to be clarified.

According to another aspect, the invention further relates to a methodfor preparing a construction material from an excavated clay soil, themethod including:

-   -   A step of measuring at least one physicochemical property of the        excavated clay soil;    -   A selection step according to a method for selecting the        composition of a construction material including a clay soil        excavated according to the invention; and    -   A step of mixing the excavated clay soil, a deflocculating        agent, and an activating agent according to the selected        composition.

Such a simple and fast method allows the emission of greenhouse gases tobe reduced during its implementation compared to the implementation of amethod for preparing a conventional construction material of thePortland cement type.

According to other optional features of the preparation method, itfurther includes:

-   -   a step of measuring physicochemical or mechanical properties of        the construction material being formed, during the mixing step,    -   a step of comparing the measured values with predetermined        values of physicochemical or mechanical properties of the        construction material being formed, and    -   when the measured values differ from the predetermined values of        the physicochemical or mechanical properties of the construction        material being formed, a step of adding at least one        complementary ingredient.

Thus, the verification of the properties of the construction materialbeing formed allows a quality control to be carried out on line, that isto say preferably in real time, so as to ensure that the constructionmaterial formed will have mechanical properties as close as possible tothe expected mechanical properties. Indeed, a deviation can beidentified at the time of mixing and corrected before the constructionmaterial is finalized and a fortiori used.

According to another aspect, the invention relates to a computer programproduct configured to run a selection method according to the invention.

According to another aspect, the invention relates to a computer programproduct configured to run a calibration method according to theinvention.

According to another aspect, the invention further relates to aconstruction material formed from an excavated clay soil characterizedin that it includes a deflocculating agent and an excavated clay soil.Preferably, the invention further relates to a construction materialformed from an excavated clay soil characterized in that it includes anexcavated clay soil, an activating agent and a deflocculating agent,said deflocculating agent accounting for at least 0.1 wt % of theconstruction material, preferably at least 0.25 wt % of the constructionmaterial.

The activating agent is not systematically found in the constructionbinder or in the site concrete since it can react with constituents ofthe excavated clay soil and be transformed. Nevertheless, in some cases,a construction material according to the invention, formed from anexcavated clay soil, may further include an activating agent.

Such a construction material formed from an excavated clay soil hasmechanical properties suitable for its use in the construction industrywhile constituting a way to reclaim the excavated clay soil.

According to other optional features of the construction materialaccording to the invention, it includes a mixture of different types ofclays.

In addition, it may include at least 2 wt % of silt particles,preferably at least 4 wt %, more preferably at least 6 wt %. The siltparticles are in particular particles with a diameter between 2 μm and50 μm.

A construction material according to the invention may include metaloxides at a content of at least 2 wt % of the construction material.

A construction material according to the invention may further includeblast furnace slag.

A construction material according to the invention may include from 30%to 80 wt % of an excavated clay soil, from 0.1% to 10 wt % of adeflocculating agent, and from 5 to 10 wt % of blast furnace slag. Inthis case, the construction material preferably corresponds to aconstruction binder.

A construction material according to the invention may include:

-   -   between 5 and 20 wt % of a raw clay from the excavated clay        soil;    -   between 0.1 and 3 wt % of a deflocculating agent;    -   between 3 and 15 wt % of an activating agent;    -   between 25 and 45 wt % of sand; and    -   between 35 and 55 wt % of aggregates;

said construction material then preferably corresponding to a siteconcrete.

As shown in the examples, the construction materials according to theinvention have improved mechanical performance.

In addition, the excavated clay soil may advantageously have beenpretreated, said pretreatment being selected from: crushing, sorting,sieving and/or drying of the excavated clay soil. The pretreatment mayfor example include fractionation.

According to another aspect, the invention relates to a method forpreparing a construction material according to the invention from anexcavated clay soil including:

-   -   a step of excavating a clay soil;    -   optionally a step of screening the excavated clay soil when the        excavated clay soil includes stones retained by a 2 cm        screening; and    -   a step of mixing the excavated clay soil, preferably the        fraction of less than 50 μm, a deflocculating agent and an        activating agent.

According to another aspect, the invention further relates to a systemfor preparing a construction material including an excavated clay soil,said system including:

-   -   At least one container including an excavated clay soil;    -   At least one container including a deflocculating agent;    -   At least one container including an activating agent;    -   A mixing device, with automated transport means between the        containers and the mixing device;    -   A control module configured to generate output signals for use        by the automated transport means to transport determined        deflocculating agent and activating agent quantities to the        mixing device.

Advantageously, the system for preparing a construction materialaccording to the invention includes a communication means configured toreceive data on a determined deflocculating agent quantity and adetermined activating agent quantity, adapted to the excavated claysoil; the control module being configured to generate output signals foruse by the automated transport means so as to transport the determineddeflocculating agent and activating agent quantities to the mixingdevice.

Preferably, the system for preparing a construction material accordingto the invention includes: A means for measuring at least onephysicochemical property of the excavated clay soil, A calculation meansable to implement a computer program configured to perform: A step ofobtaining a measured value of at least one physicochemical property ofthe excavated clay soil; and A step of determining a deflocculatingagent quantity and an activating agent quantity adapted to the excavatedclay soil based on a comparison of the one or more measured values withreference values.

In particular, the invention further relates to a system for preparing aconstruction material including an excavated clay soil, said systemincluding:

-   -   At least one container including an excavated clay soil;    -   At least one container including a deflocculating agent;    -   At least one container including an activating agent;    -   A mixing device, with automated transport means between the        containers and the mixing device;    -   A means for measuring at least one physicochemical property of        the excavated clay soil;    -   A calculation means adapted to implement a computer program        configured to perform:        -   A step of obtaining a measured value of at least one            physicochemical property of the excavated clay soil, and        -   A step of determining a deflocculating agent quantity and an            activating agent quantity suitable for the excavated clay            soil based on a comparison of the one or more measured            values with reference values; and    -   A control module configured to generate output signals for use        by the automated transport means so as to transport the        determined deflocculating agent and activating agent quantities        to the mixing device.

Such a system allows the automated formation of a construction binder orpossibly a site concrete (with the addition of fillers) from excavatedclay soil, with these construction materials having mechanicalproperties equivalent to the mechanical properties of conventionalmaterials with a much larger carbon footprint.

Other advantages and features of the invention will appear upon readingthe following description given by way of illustrative and non-limitingexample, with reference to the appended figures:

FIG. 1 represents the steps of a method for selecting the composition ofa construction material including an excavated clay soil according toone embodiment of the present invention. The steps in dotted lines areoptional.

FIG. 2 represents the steps of a method for calibrating a calculationalgorithm for determining the composition of a site constructionmaterial. The steps in dotted lines are optional.

FIG. 3 represents the steps of a method for preparing a constructionmaterial from an excavated clay soil. The steps in dotted lines areoptional.

FIG. 4 represents a method for preparing a construction materialaccording to one embodiment of the invention.

FIG. 5 represents a method for preparing a construction materialaccording to one embodiment of the invention. The steps in dotted linesare optional.

FIG. 6 represents a diagram showing a functional architecture of thesystem for preparing a construction material including an excavated claysoil according to the invention. The solid arrows represent transportmeans and the dotted arrows represent data transfer or instructions, inparticular to said transport means.

Aspects of the present invention shall be described with reference toflowcharts and/or block diagrams of methods, apparatus (systems) andcomputer program products according to embodiments of the invention. Inthe figures, the flowcharts and block diagrams illustrate thearchitecture, the functionality and the operation of possibleimplementations of systems, methods and computer program productsaccording to various embodiments of the present invention.

In this respect, each block in the flowcharts or block diagrams mayrepresent a system, device, module, or code, which comprises one or moreexecutable instructions for implementing the one or more specifiedlogical functions. In some implementations, the functions associatedwith the blocks may appear in a different order than shown in thefigures. For example, two blocks shown in succession may, in fact, beexecuted substantially simultaneously, or the blocks may sometimes beexecuted in reverse order, depending on the functionality involved. Eachblock in the flow diagrams and/or flowchart, and combinations of blocksin the flow diagrams and/or flowchart, may be implemented by specialhardware systems that perform the specified functions or acts or performcombinations of special hardware and computer instructions.

DESCRIPTION OF THE INVENTION

In the remainder of the description, the expression “clay soil” must beunderstood as corresponding to a soil originating from a clay-containingsoil, or more generally from a loose formation with a fine particlesize, and therefore containing one or more rocky materials based onhydrated silicates or aluminosilicates of a lamellar structure. Inparticular, a clay soil can correspond to soil such as sandy-clayey siltsoil, clayey-silty soil, clayey-sandy soil, clay soil. Preferably, aclay soil includes at least 25 wt % of clay, preferably at least 30 wt %of clay, more preferably at least 40 wt % of clay. The clay content byweight can be determined by standard methods of the prior art such asthe particle size method described in the NF X31-107 standard.Furthermore, preferably, a clay soil in the framework of the inventionincludes at most 95 wt % clay, preferably at most 90 wt % clay, morepreferably at least 80 wt % clay.

The expression “excavated clay soil” corresponds, within the meaning ofthe invention, to a clay soil obtained following a step where the soilhas been dug up, for example during leveling and/or earthworkoperations, with the aim of constructing, building, or backfilling. Inparticular, within the meaning of the invention, the excavated clay soilmay or may not be moved from the production site. Preferably andaccording to an advantage of the invention, the excavated soil is usedon the production site or at a distance of less than 200 km. Inaddition, advantageously, the clay soil excavated within the frameworkof the invention is a raw excavated clay soil, that is to say it has notundergone a calcination step. In particular, that is, it has not beensubjected to any heat pretreatment. For example, this corresponds to aclay soil which has not undergone a rise in temperature higher than 300°C., preferably higher than 200° C., and more preferably a temperaturehigher than 150° C. Indeed, the raw clay can undergo a heating steprequiring a temperature rise generally substantially equal to 150° C.,but no calcination step. Conventionally used clay has a relativelyconstant particle size profile with sizes below 2 μm. Excavated claysoil can have different particle size profiles. In the framework of theinvention, an excavated clay soil may include particles of a sizegreater than 2 μm, preferably greater than 20 μm, more preferablygreater than 50 μm, and for example greater than 75 μm as determinedaccording to the ASTM D422-63 standard. Preferably, the excavated claysoil does not include any aggregate larger than 2 cm as determinedaccording to the NF EN 933-1 standard.

The term “wt %” in relation to excavated clay soil, composition, binder,or site concrete shall be understood as a proportion to the dry weightof the composition, binder, or site concrete. The dry weight correspondsto the weight before the addition of water, which is for examplenecessary to form a construction material.

The expression “construction material”, within the meaning of theinvention, corresponds to a construction binder or a site concrete. Thesite concrete will in particular include fillers such as aggregatesand/or sand.

By “deflocculating agent” is meant any compound which, in aqueoussuspension, will dissociate aggregates and colloids. Deflocculatingagents have been used, for example, in the context of oil drilling orextraction to make the clay more fluid and facilitate extraction ordrilling.

By “activating agent” is meant any composition having the function ofaccelerating the dispersion of an aluminosilicate source promoting theformation of stable hydrates with low solubility and the formation of acompact structure with these hydrates, thereby increasing the mechanicalstrength of materials incorporating such an activating composition.

The term “particle size”, within the meaning of the invention,corresponds to the distribution of the elements and particles of theclay soil according to the relative proportion by weight of thedifferent classes of particles, identified by their size andconstituting the mineral skeleton of the soil. Five particle sizeclasses exist:—Clays (0 to 2 micrometers)—Fine silts (2 to 20micrometers)—Coarse silts (20 to 50 micrometers)—Fine sands (50 to 200micrometers)—Coarse sands (200 to 2000 micrometers).

The expression “nature of the clays” corresponds, within the meaning ofthe invention, to the chemical and/or mineralogical properties of theclays. This corresponds in particular to the chemical composition of theclays, but also to their mineralogy and their physical characteristics(such as specific surface, porosity, morphology). For example, this maycorrespond to the identification of the clay by its common name (e.g.kaolinite, illite, montmorillonite, smectite, bentonite, chlorite andvermiculite).

The expression “metallic trace elements” corresponds, within the meaningof the invention, to metallic chemical elements and in particular theycorrespond, within the meaning of the invention, to metals selectedfrom: iron, lead, mercury, uranium, chromium, copper, cadmium, silver,gold, zinc, nickel, or titanium.

the term “substantially equal”, within the meaning of the invention,corresponds to a value varying by less than 20% with respect to thecompared value, preferably by less than 10%, even more preferably byless than 5%.

By “model” or “rule” or “calculation algorithm”, is to be understood,within the meaning of the invention, a finite sequence of operations orinstructions making it possible to select deflocculating agent andactivating agent quantity values, that is to say, for example, to formpreviously defined groups Y associated with scores or categories as afunction of correlation with deflocculating agent D and activating agentA quantities, on the one hand, and one or more values of physicochemicalproperties of excavated clay soil E. The implementation of this finitesequence of operations makes it possible, for example, to assign a labelY₀ to an observation described by a set of characteristics D₀, A₀, E₀thanks, for example, to the implementation of a function f capable ofreproducing Y having observed D, A and E.Y=f(D,A,E)+e

-   -   where e symbolizes noise or measurement error.

Herein, Y can for example be the ability (yes/no) to form a constructionmaterial.

Advantageously, the calculation algorithm can establish previouslydefined groups, associate other values such as values of mechanicalproperties M of the construction material that can be formed from thesequantities. Thus, with the formula “M=f(D,A,E)+e”, it is possible toselect quantity values for forming construction materials withpredetermined mechanical properties.

By “supervised learning method” is meant, within the meaning of theinvention, a method for defining a function f from a base of n labeledobservations (X_(1 . . . n), Y_(1 . . . n), D_(1 . . . n),A_(1 . . . n), E_(1 . . . n)) where, for example, Y=f(D,A,E)+e orM=f(D,A,E)+e.

By “process”, “calculate”, “determine”, “display”, “extract”, “compare”,or more broadly an “executable operation” is meant, within the meaningof the invention, an action performed by a device or a processor unlessthe context indicates otherwise. In this respect, operations refer toactions and/or processes in a data processing system, such as a computersystem or electronic computing device, which manipulates and transformsdata represented as physical (electronic) quantities in the memories ofthe computer system or other devices for storing, transmitting, ordisplaying information. In particular, calculation operations areperformed by the processor of the device, the data produced are writteninto a corresponding field in a data memory and this field or thesefields can be returned to a user for example through an adapted HumanMachine Interface, such as by way of non-limiting examples a screen of aconnected object, formatting such data. These operations may be based onapplications or software.

The terms or expressions “application”, “software”, “program code”, and“executable code” mean any expression, code, or notation, of a set ofinstructions intended to cause a data processing to perform a particularfunction directly or indirectly (for example after a conversionoperation into another code). Exemplary program codes may include, butare not limited to, a subprogram, a function, an executable application,a source code, an object code, a library and/or any other sequence ofinstructions designed for being performed on a computer system.

By “processor” is meant, within the meaning of the invention, at leastone hardware circuit configured to perform operations according toinstructions contained in a code. The hardware circuit may be anintegrated circuit. Examples of a processor include, but are not limitedto, a central processing unit, a graphics processor, anapplication-specific integrated circuit (“ASIC” according to anAnglo-Saxon terminology), and a programmable logic circuit. A singleprocessor or several other units may be used to implement the invention.

By “coupled” is meant, within the meaning of the invention, connected,directly or indirectly, with one or more intermediate elements. Twoelements may be coupled mechanically, electrically, or linked by acommunication channel.

The expression “human-machine interface”, within the meaning of theinvention, corresponds to any element allowing a human being tocommunicate with a computer, in particular and without that list beingexhaustive, a keyboard and means allowing in response to the commandsentered on the keyboard to perform displays and optionally to selectwith the mouse or a touchpad items displayed on the screen. Anotherembodiment is a touch screen for selecting directly on the screen theelements touched by the finger or an object and optionally with thepossibility of displaying a virtual keyboard.

In the claims, the term “comprise” or “include” does not exclude otherelements or other steps.

In the following description, the same references are used to designatethe same elements. The reference signs should not be understood aslimiting the scope of the invention. In addition, the different featurespresented and/or claimed can be advantageously combined. Their presencein the description or in different dependent claims, do not exclude thispossibility.

As mentioned above, the current situation is that there is plenty ofexcavated soil, which is often considered as waste and thereforeconstitutes, when developing a site, an additional burden fordevelopers. Such management, and in particular the pollution that may begenerated by the transport of these excavated soils, adds to thepollution generated by the preparation of conventional cement (e.g.Portland).

Faced with this observation, the inventors have identified a method forselecting a composition for a construction material using excavated claysoil and making it possible to obtain a construction binder withmechanical properties similar to those of conventional cement (e.g.Portland). Using this method, they are able, as will be shown in theexamples, to generate a construction binder which could beadvantageously, but not limitatively, used as a replacement for Portlandcement, lime, or CSA. Thus, the waste (i.e. excavated clay) combined inparticular proportions with a deflocculating agent and an activatingagent, can become a raw material in a construction method.

Moreover, given its preparation method, on the one hand, and the use ofexcavated clay soil, the construction material according to theinvention has the advantage of having a carbon footprint at least twotimes lower than most of the construction materials, or hydraulicbinder, most used in the world today (i.e. Portland cement). Indeed, aconstruction material according to the invention is mainly made of aclay soil and has a zero or lower clinker content than equivalentproducts and allows, with equivalent mechanical properties, to reduceCO₂ emissions and production costs.

Moreover, the clay soil has preferably not undergone a calcination step,an energy-consuming step which also generates the emission of greenhousegases and more particularly of carbon dioxide.

Finally, advantageously, as will be presented in the examples, aconstruction binder according to the invention allows constructionmaterials having mechanical properties at least equivalent to Portlandcement and much superior to “low carbon” materials, such as thosedescribed above, to be produced.

Thus, according to a first aspect, the invention relates to a method 100for selecting the composition of a construction material including anexcavated clay soil. Since the construction binder may subsequently beused to form a site concrete, for example, following the addition of afiller, the selection method 100 may alternatively correspond to amethod 100 for selecting the composition of a site concrete.

In particular, for the preparation of a construction material from theexcavated clay soil to be possible, the construction materialcomposition must include deflocculating agent and activating agentquantities adapted to the excavated clay soil.

To this end, a method according to the invention, preferably implementedby a computer device including a calculation module, may include a stepof receiving 130, from the calculation module, a measured value of atleast one physicochemical property of an excavated clay soil; and a stepof selecting 170, by the calculation module, a deflocculating agentquantity and an activating agent quantity adapted to the excavated claysoil.

In addition, a method according to the invention may include steps suchas: previously treating 110 the excavated clay soil, measuring 120physicochemical properties of the excavated clay soil, receiving 140desired mechanical property value of the construction material,generating 150 a plurality of combinations of deflocculating agent andactivating agent quantity values, determining 160 a desired mechanicalproperty value of the construction material, or determining at least onephysicochemical or mechanical property value of the constructionmaterial being formed.

As illustrated in FIG. 1 , the selection method according to theinvention may include a step of previously treating 110 the excavatedclay soil. Thus, advantageously, the one or more measurement values areobtained from a sample of excavated clay soil having undergone apretreatment step 110 of the excavated clay soil.

This pretreatment step may for example include or consist offractioning, crushing, sorting (e.g. according to the color), sieving,and/or drying of the excavated clay soil.

In particular, since, in the framework of the present invention, theclay soil is an excavated soil, it may include coarse elements orfractions of high dimensions which would be advantageously removed inthe first stages of the method. Thus, in particular, the methodaccording to the invention may include removing elements having at leastone dimension greater than 1 cm (for centimeter), preferably removingelements having at least one dimension greater than 0.2 cm. Preferably,the method according to the invention may include removing elementshaving at least a size greater than 1 cm, preferably greater than 475 μm(for micrometer), more preferably greater than 75 μm as determinedaccording to the ASTM D422-63 standard.

In addition, the method according to the invention may include a step ofmeasuring 120 at least one physicochemical property of an excavated claysoil. This step is preferably carried out on a sample of excavated claysoil and can be performed on site or in a specialized laboratory.Indeed, depending on the one or more physicochemical propertiesmeasured, it will be possible or not to have transportable instruments.

The measuring step 120 may include, for example, a step of measuring:

-   -   the clay content in the excavated clay soil, measured for        example by a particle size method such as that described in the        NF X31-107 standard;    -   the nature of the clays, obtained for example by X-ray        diffractometry;    -   the content of impurities and in particular of metallic trace        elements, obtained for example by elemental analysis using an        ICP-MS apparatus;    -   the salinity with a conductivity meter measuring the        conductivity of a clay soil wash water;    -   the pH using a pH meter measuring the pH of a clay soil wash        water; and    -   the total exchange capacity of the clay in the excavated clay        soil measured for example by the so-called methylene blue method        according to the NF EN 933-9+A1 standard.

Thus, the measuring step 120 may, for example, include using a pH meter,an X-ray diffractometer, a conductivity meter, an electron microscope, amercury porosimeter, a spectrofluorometer, an ICP-MS (in English:Inductively Coupled Plasma Mass Spectrometry), HPLC-MS (liquidchromatography coupled to mass spectrometry), GC-MS (gas chromatographycoupled to mass spectrometry), measuring the specific surface by the BETmethod (Specific surface measurement, for Brunauer-Emmett-Teller), agranulometer, or a TGA (for thermogravimetric analysis) rheometer.

The method according to the invention includes a step of receiving 130 ameasured value of at least one physicochemical property of an excavatedclay soil. In particular, this step can be implemented by thecalculation module of the digital device.

The physicochemical property of the excavated soil, the measured valueof which is received, can be selected from: the content of clays in theexcavated clay soil, the nature of the clays, the particle size, theimpurity content, the presence of pollutants, the liquidity limit, theplasticity limit, the content of metal oxides, the salinity, the pH, andthe total exchange capacity of the clay in the excavated clay soil. Forexample, the physicochemical property of the excavated soil, themeasured value of which is received, may be selected from: the contentof clays in the excavated clay soil, the nature of the clays, theparticle size, the content of impurities, the content of metal oxides,the salinity, the pH, and the total exchange capacity of the clay in theexcavated clay soil. Preferably, the physicochemical property of theexcavated soil, the measured value of which is received, can for examplebe selected from: the content of clays in the excavated clay soil, theliquidity limit, and the plasticity limit. More preferably, thephysicochemical property of the excavated soil, the measured value ofwhich is received, includes the content of clays in the excavated claysoil.

In particular, the content of impurities may correspond to the contentof metals and advantageously of metal oxides such as: iron oxide oraluminum oxide.

Preferably, measured values of at least two physicochemical propertiesof an excavated clay soil are received, more preferably at least three,and even more preferably at least four. Indeed, depending on the numberof physicochemical properties taken into account, the result of theselection method can be of better quality.

The one or more physicochemical properties are physicochemicalproperties of widely studied soils such as pH, particle size, content ofclays.

In particular, the method according to the invention includes receiving130 a combination of measured values selected from:

-   -   the content of clays in the excavated clay soil and the nature        of the clays;    -   the content of clays and the total exchange capacity of the clay        in the excavated clay soil;    -   The content of clays and the quantity of pollutants;    -   the pH and the content of clays of the excavated clay soil; or    -   the total exchange capacity of the clay in the excavated clay        soil and the particle size.

Further, as shown in FIG. 1 , the method according to the invention mayinclude receiving 140 a desired mechanical property value of aconstruction material.

Indeed, in addition to selecting the composition of a constructionmaterial, the method according to the invention can advantageously makeit possible to select a composition of a construction material allowingthe preparation of a construction material which will have givenmechanical properties. Thus, a user will be able to select the mostappropriate quantities to obtain a construction material that meetshis/her needs.

The desired mechanical properties of the construction material can forexample be selected from: compressive strength, drying shrinkage,setting time, flexural strength, tensile strength, Young's modulus,Poisson's ratio.

For example, the method according to the invention may include receivinga desired compressive strength value for the construction material. Thisvalue can for example consist of a lower bound (e.g. 20 MPa, forMegaPascal, or 30 MPa) or a fixed value (e.g. 40 MPa).

Preferably, when the method according to the invention includesreceiving 140 a desired mechanical property value of the constructionmaterial, the step of selecting 170 the deflocculating agent andactivating agent quantities further includes excluding 171 thedeflocculating agent and activating agent quantities which will notallow the construction material to exhibit the desired mechanicalproperty value. For example, this may correspond to a selection via thecalculation algorithm of all values of A and D which allow, from ameasured value of E, to yield a value of M=40 MPa. Alternatively, in theabsence of a calculation algorithm, this may include filtering out allvalues from a database for which the value of M is less than 30 MPa.

The step of receiving 130 a measured value of at least onephysicochemical property of an excavated clay soil may be followed by astep of generating 150 a plurality of combinations of deflocculatingagent quantity values, on the one hand, and activating agent quantityvalues, on the other hand. Following the generation of this plurality ofvalues, the calculation module may implement a value selection step 170as described below.

In addition, the method according to the invention may include a step ofdetermining 160 at least one physicochemical property or mechanicalproperty value expected for the construction material. This step is forexample implemented by a calculation module.

From the measured values of physicochemical properties of the excavatedclay soil and from the generated deflocculating agent and activatingagent quantity values, it is then possible to determine a value of amechanical property of a construction material formed from the excavatedsoil and the considered deflocculating agent and activating agentquantities.

The method according to the invention includes a step of selecting 170 adeflocculating agent quantity and an activating agent quantity adaptedto the excavated clay soil. This step can for example be implemented bya calculation module.

The deflocculating agent and activating agent quantity may correspond toa volume, a mass or a proportion. Preferably, the quantity correspondsto a proportion relative to an excavated clay soil quantity to be addedto the construction material composition. Alternatively, if the quantitycorresponds to a volume or mass, it is then associated with a quantityof excavated clay soil to be added to the construction materialcomposition.

In addition, selecting 170 a deflocculating agent quantity and anactivating agent quantity may include determining the nature of thedeflocculating agent and/or the activating agent to be added. Forexample, the nature of these agents may correspond to a family ofchemical molecules or to a particular chemical molecule or combinationof molecules.

Indeed, the deflocculating agent can be a combination of molecules andthe selection of a deflocculating agent quantity can then correspond tothe selection of quantity of each of the molecules constituting thedeflocculating agent. The same applies to the activating agent, whichmay be one molecule or a plurality of molecules.

Advantageously, the selection is made based on a comparison of the oneor more measured values of the physicochemical property of an excavatedclay soil with reference values. In particular, the reference valuesinclude correlations between measured values of at least onephysicochemical property of a clay soil and deflocculating agent andactivating agent quantities adapted to said clay soil to form aconstruction material.

Deflocculating Agent

Many compounds can act as deflocculating agents and many are generallyknown to the one skilled in the art.

In the framework of the invention, the deflocculating agent is inparticular a nonionic surfactant such as a polyoxyethylene ether. Thepolyoxyethylene ether may for example be selected from: apoly(oxyethylene) lauryl ether.

The deflocculating agent may also be an anionic agent such as an anionicsurfactant. In particular, the anionic agent may be selected from:alkylaryl sulfonates, amino alcohols, carbonates, silicates, fattyacids, humates (e.g. sodium humates), carboxylic acids, lignosulfonates(e.g. sodium lignosulfonates), polyacrylates, phosphates, orpolyphosphates such as sodium hexametaphosphate, sodiumtripolyphosphate, sodium orthophosphate, carboxymethylcelluloses, andmixtures thereof.

The deflocculating agent may also be a polyacrylate. It may then beselected, for example, from sodium polyacrylate and ammoniumpolyacrylate.

The deflocculating agent may also be an amine selected, for example,from: 2-amino-2-methyl-1-propanol; mono-, di-, or triethanolamine;isopropanolamines (1-amino-2-propanol, diisopropanolamine, andtriisopropanolamine), and N-alkylated ethanolamines.

The deflocculating agent may also be a silicate such as sodium silicate,sodium metasilicate, or sodium trisilicate.

Alternatively, as discussed above, the deflocculating agent may be amixture of compounds, such as a mixture including at least two compoundsselected from: nonionic surfactant, anionic agent, polyacrylate, amine,and organophosphorus compound.

In particular, the deflocculating agent may be a mixture of sodiumsilicate and sodium carbonate. Preferably, the deflocculating agent isselected from: a lignosulfonate (e.g. sodium lignosulfonate), apolyacrylate, a humate, and mixtures thereof.

The deflocculating agent is preferably in the form of a salt.

However, the invention is not limited to the above-mentioneddeflocculating agents, any type of deflocculating agent known to the oneskilled in the art may be used instead of the above-mentioneddeflocculating agents.

Activating Agent

It is the activating agent, in conjunction with the excavated clay soiland the deflocculating agent, that will give the construction materialits mechanical properties of interest.

Without being limited by the theory, the activating agent can allow theconstitution of a network between the clay sheets which will confer theconstruction material according to the invention its mechanicalproperties.

In particular, the activating agent may include metal oxides and/or bean alkaline activating composition.

Preferably, the metal oxides are transition metal oxides. Morepreferably, the metal oxides are selected from: iron oxides such as FeO,Fe₃O₄, Fe₂O₃, Fe₂O₃, alumina Al₂O₃, manganese(II) oxide MnO,titanium(IV) oxide TiO₂, and mixtures thereof.

The metal oxides may preferably be derived from a composition of blastfurnace slag, for example, formed during the production of pig iron fromiron ore.

The metal oxides are present at a content of at least 2 wt % of theconstruction material, preferably at least 5 wt % of the constructionmaterial, more preferably at least 10 wt % of the construction material.

When the activating agent is an alkaline activating composition. Thealkaline composition may preferably include a compound having a pKagreater than or equal to 10, more preferably greater than or equal to12, even more preferably substantially equal to 14.

The alkaline composition may, for example, include an organophosphoruscompound such as sodium tripolyphosphate, designated by the acronymNaTPP.

In particular, the activating agent may include a mixture of sodiumhydroxide and sodium silicate. Advantageously, the activating agent maybe an alkaline activating composition further including metal oxides. Aswill be shown in the examples, construction binders prepared from suchan activating agent have good mechanical properties. Thus, preferably,the activating agent may include metal oxides and at least one compoundhaving a pKa greater than or equal to 10.

In addition, the selection step 170 may include determining 172 anadditive quantity to be incorporated into the construction materialcomposition. Indeed, the selection method according to the invention canlead to a construction material composition including some additives indetermined concentrations. These additives allow the chemical and/ormechanical properties of the final construction material to be modified.

The additive is selected, for example, from: a plasticizer, a syntheticor natural rheological holding agent, an anti-shrinkage agent, a waterretention agent, an air entraining agent, a synthetic resin, a pigment,and mixtures thereof.

The plasticizer may, for example, be a polyacrylate, a polynaphthalenesulfonate, a polycarboxylate, or a polyphosphonate.

In addition, the selection step 170 may include determining 173 a fillerquantity to be incorporated into the mix so as to form a site concrete.These fillers allow the mechanical properties of the final constructionmaterial to be modified.

The filler can, for example, be selected from recycled or non-recycledaggregates, powders, sand, gravel, crushed concrete, and/or fibers.

The fibers are selected, for example, from: vegetable fibers such ascotton, flax, hemp, cellulose, bamboo, miscanthus fibers, syntheticfibers such as metal, glass, carbon, polypropylene fibers, and mixturesthereof. The presence of fibers can allow the formation of aconstruction material with improved mechanical and insulatingproperties.

Advantageously, and as previously discussed, the step of determining 170a deflocculating agent quantity and an activating agent quantity adaptedto the excavated clay soil includes implementing a previously calibratedcalculation algorithm.

This calculation algorithm may have been built from different learningmodels, in particular partitioning, supervised, or unsupervised models.

An unsupervised statistical learning model can, for example, be selectedfrom an unsupervised Gaussian mixture model, a hierarchical bottom-upclassification (Hierarchical clustering Agglomerative in Anglo-Saxonterminology), a hierarchical top-down classification (hierarchicalclustering divisive in Anglo-Saxon terminology).

A statistical supervised learning model can, for example, be selectedamong kernel methods (e.g. Support Vector Machines SVM, Kernel RidgeRegression) described for example in Burges, 1998 (Data Mining andKnowledge Discovery. A Tutorial on Support Vector Machines for PatternRecognition), set methods (e.g. Bagging, Boosting, Decision Trees,Random Forest) described, for example, in Brieman, 2001 (MachineLearning. Random Forests), or neural networks described, for example, inRosenblatt, 1958 (The perceptron: a probabilistic model for informationstorage and organization in the brain).

Preferably, the previously calibrated calculation algorithm has beenobtained by implementing a statistical supervised learning method.

Thus, according to another aspect, the invention relates to a method 200for calibrating a calculation algorithm. This calculation algorithm isparticularly dedicated to the determination of the composition of aconstruction material. A calibration method according to the inventioncan in particular be implemented by a digital device comprising alearning module.

As illustrated in FIG. 2 , such a calibration method according to theinvention includes a step of receiving 230 a measured value of at leastone physicochemical property of an excavated clay soil.

Preferably, several measured values and in particular values of at leasttwo, more preferably at least three, and even more preferably at leastfour physicochemical properties of an excavated clay soil, are received.Indeed, depending on the number of physicochemical properties taken intoaccount, the calibration method will be of better quality.

The calibration method according to the invention also includes a stepof receiving 240 a deflocculating agent quantity value and an activatingagent quantity value. These values correspond to the quantities ofagents which, once added to the excavated clay soil, make it possible toform a construction material.

The deflocculating agent and activating agent quantity may correspond toa volume, a mass, or a proportion. Preferably, the quantity correspondsto a proportion relative to an excavated clay soil quantity to be addedto the construction material composition. Alternatively, if the quantitycorresponds to a volume or mass, it is then associated with a quantityof excavated clay soil to be added to the construction materialcomposition. In addition, receiving 240 deflocculating agent andactivating agent quantity values may include receiving the nature of thedeflocculating agent and/or the activating agent. For example, thenature of these agents may correspond to a family of chemical moleculesor to a particular chemical molecule or to a combination of molecules.

These values may have been obtained through tests that will be describedin the examples section. Only those quantities of agents which enablethe formation of a construction material are included in the calibrationmethod.

Indeed, the calibration method may include a step of forming 250 aconstruction material according to the received values. Alternatively,and preferably, a plurality of combinations of agent quantity valueshave been tested on a plurality of excavated clay so as to form adatabase that can be used as input data to the calibration method.

The method then includes a step of creating 270 a correlation betweenthe received measured values in order to calibrate a calculationalgorithm. This correlation step, based on measured values, allows acalculation algorithm to be built from a statistical learning model.Thus, the calculation algorithm can take the form of a function fin anequation of the typeY=f(E,A,D)

Preferably, as shown in FIG. 2 , prior to the creation step 270, thecalibration method according to the invention may further include a stepof receiving 260 a measured value of at least one mechanical property ofthe formed construction material. In fact, in addition to using theagent quantity values and the one or more values of the physicochemicalproperty of the excavated clay soil, the calibration method according tothe invention can use one or more measured values of the resultingconstruction material. Thus, the calculation algorithm can take the formof a function f in an equation of the type:M=f(E,A,D)

Preferably, several measured values, and in particular values of atleast two, more preferably at least three and even more preferably atleast four physicochemical properties of the construction material, arereceived 260.

In addition, as illustrated in FIG. 2 , the calibration method accordingto the invention may include a step of pretreating 210 a sample of claysoil that may come before a step of measuring 220 at least onephysicochemical property of a clay soil. In addition, once thecorrelation is established, it can be saved 280 on a storage medium suchas a RAM or non-volatile memory.

Advantageously, a calibration method according to the invention mayinclude a step of updating 290 the calculation algorithm by repeatingthe preceding steps described above and at least: Receiving 230 ameasured value of at least one physicochemical property of an excavatedclay soil, Receiving 240 a deflocculating agent quantity and anactivating agent quantity which when added to the excavated clay soilform a construction material, and Creating 270 a correlation between thereceived measured values so as to calibrate a calculation algorithm.

According to another aspect, the invention relates to a method 300 forpreparing a construction material from an excavated clay soil.

Such a method according to the invention, illustrated in FIG. 3 , hasthe advantage of being a so-called low-carbon method, that is to say amethod the greenhouse gas emissions, such as carbon dioxide emissions inparticular, of which are reduced compared to the greenhouse gasemissions of known methods for preparing construction binders. Suchreductions in greenhouse gas emissions are linked in particular to theabsence of a calcination stage, which is particularly energy-intensive.

Furthermore, the preparation of a construction binder according to theinvention may allow the preparation of a site concrete made at least inpart from raw material from the construction site. Such characteristicsfurther reduce the environmental footprint of the concrete produced.Once a deflocculating agent quantity and an activating agent quantityadapted to the excavated clay soil have been selected, it is possible,according to conventional methods, to proceed with the preparation of aconstruction material from an excavated clay soil.

The preparation method according to the invention may include a step ofmeasuring 310 at least one physicochemical property of the excavatedclay soil.

Such a step may be performed well before the mixing step 340. This isthe case, for example, if preliminary studies are carried out and thereis no need to use the excavated soil quickly. Alternatively, the step ofmeasuring 310 at least one physicochemical property of the excavatedclay soil may be performed just before the steps of selecting 100 thecomposition of a construction material, corresponding to a step ofimplementing the method 100 according to the invention, and mixing 340.This is the case, for example, in an automated method for thepreparation of a construction material from an excavated clay soil,where the excavated clay soil is analyzed in line with a transportablemeasuring device and then mixed continuously with selected agentquantities so as to form a construction material in a very short time.

Preferably, several measured values and in particular values of at leasttwo, more preferably at least three, and even more preferably at leastfour physicochemical properties of the excavated clay soil, arereceived.

Furthermore, as illustrated in FIG. 3 and FIG. 4 , a preparation methodaccording to the invention may include selecting 100 the composition ofa construction material including an excavated clay soil according tothe invention.

In addition, it may include a step of mixing 340 the excavated claysoil, a deflocculating agent, and an activating agent according to theselected composition.

In the mixing step, water can be added in such a way that the ratio ofthe mass of water to the mass of construction material is less than 1,and for example between 0.4 and 0.8. In addition, water canadvantageously be added after the excavated clay soil and thedeflocculating agent have been dry-mixed.

Thus, preferably, the method according to the invention may include amixing step so as to obtain a suspension of dispersed or deflocculatedexcavated clay soil. When mixing, preferably, the deflocculating agentis added before the activating agent so that the activating agent ismixed with dispersed or deflocculated excavated clay soil.

This mixing step 340 of the clay suspension can advantageously, but notlimitatively, be carried out in a device selected among: a mixer and atruck mixer or more generally within any device adapted to mix a claysoil.

Preferably, the preparation method may include a step of screening 330the excavated clay soil. This screening step occurs before the mixingstep 340 and before or after the measuring step 310. In particular, itis carried out in such a way as to remove aggregates, the diameter ofwhich is greater than 20 mm (for millimeter).

In a broader sense, the preparation method may include a step ofpreparing the excavated clay soil, where said preparation may include,for example: drying, grinding, sieving, storing.

Preferably, the pretreatment or screening step includes at least onefractionation such as sieving, more preferably fractionation such as a50 μm sieving. Advantageously, but not limitatively, the elements orparticles thus sifted, such as for example sand and/or aggregatefractions, can be reused in the formulation of the construction materialand in particular of the site concrete. The most interesting fractionfor the preparation of the construction material is the fraction notretained by the sieve. Thus, a method 300 according to the invention forpreparing a construction material from an excavated clay soil willadvantageously include a step of fractioning 335 the optionally siftedexcavated clay soil, said fractioning preferably being carried out at 50μm.

Alternatively, the excavated clay soil may not be pretreated, and all ofthe clay soil is used to obtain the construction material. In this case,the method allows a site concrete to be produced.

This advantageously makes it possible to reclaim all the excavated claysoil, in particular in the case where the physicochemical propertiesassociated with the said excavated clay soil are sufficient to obtain aconstruction material with the desired mechanical properties. In thisway, all the soil can be reclaimed from the outset without the need toisolate the clay to process it and formulate the material.

As illustrated in FIG. 5 , a method 300 according to the invention forpreparing a construction material from an excavated clay soil willadvantageously include:

-   -   a step of excavating 320 a clay soil;    -   a step of screening 330 the excavated clay soil when the        excavated clay soil includes stones retained by a 2 cm        screening;    -   a step of mixing 340 the excavated clay soil, preferably the        fraction of less than 50 μm, a deflocculating agent and an        activating agent.

In addition, the preparation method can advantageously include a step oftreating the pollutants. Such a pollutant treatment step allows theconcentration of pollutants, such as traces of metallic elements,hydrocarbons (e.g. Polycyclic Aromatic Hydrocarbons and C10 to C40), PCB(Polychlorinated Biphenyls), BTEX (benzene, toluene, ethylbenzene,xylenes), TOC (total organic carbon), to be reduced in the excavatedclay soil.

Furthermore, conventionally, before, concomitantly with, or after theaddition of the activating composition, a method according to theinvention may include adding additives or fillers for modifying themechanical properties of the final construction material.

Advantageously, the preparation method may include measuring 350 one ormore values of physicochemical or mechanical properties of theconstruction material, during the mixing step (i.e. the constructionmaterial is being formed), comparing 360 the measured values withpredetermined values of physicochemical or mechanical property of theconstruction material being formed.

Thus, it is possible to carry out a quality control of the constructionmaterial being formed.

Furthermore, when the measured values differ from predetermined valuesof physicochemical or mechanical properties of the construction materialbeing formed, the preparation method may include a step of adding 370 atleast one complementary ingredient.

Herein, the complementary ingredient may for example be selected from: adeflocculating agent, an activating agent, and an excavated clay soil soas to modify the predetermined composition. The complementary ingredientmay also be selected from: additives or fillers as described above. Thisensures that the construction material being formed will have mechanicalproperties as close as possible to the expected mechanical properties.Indeed, a deviation can be identified at the time of mixing andcorrected before the material is used.

Furthermore, as illustrated in FIG. 4 , the method is completed by astep of recovering 380 the formed construction material.

According to another aspect, the invention relates to a system 400 forpreparing a construction material including an excavated clay soil.Alternatively as discussed, the invention relates to a system 400 forpreparing a site concrete including an excavated clay soil. Such amethod according to the invention, illustrated in FIG. 5 , may includecontainers 410, 420, 430 for the various components of the constructionmaterial. For example, it may include at least one container 410 for anexcavated clay soil, at least one container 420 for a deflocculatingagent, and at least one container 430 for an activating agent. Inaddition, it may include at least one container 440 for fillers and/oradditives. In addition, the system may include a cleaning container forholding a cleaning solution.

Especially in the case of the excavated clay soil, the container 410 maynot be an object but only a place where the excavated clay soil isstored. A container can also be selected from a tank, a container, abin, a silo.

In addition, the system according to the invention includes a mixingdevice 450. In particular, such a device is capable of homogenizingand/or stirring the precursor ingredients of the construction binder.

This mixing device 450 is in particular coupled to automated transportmeans (represented by an arrow between the containers 410, 420, 430,440, and the mixing device 450, respectively) positioned between thecontainers 410, 420, 430, and the mixing device 450. These transportmeans can be, for example, flexible or non-flexible pipes, belts,conveyors, or augers. In addition, in combination with the transportmeans, the system may include pumps, valves, solenoid valves, and flowrestrictors. In particular, the flow restrictors may be arranged infunctional switching with each of the transport means to independentlyregulate the quantity of each of the ingredients delivered to the mixingdevice 450.

In addition, the system according to the invention may include a meansfor measuring 460 at least one physicochemical property of the excavatedclay soil. Such a measuring means 460 may be, for example, a pH meter,an X-ray diffractometer, a conductivity meter, an electron microscope, amercury porosimeter, a spectrofluorometer, an ICP-MS, an HPLC-MS, aGC-MS, the measurement of the specific surface area by the BET method, agranulometer, or a rheometer.

In addition, the system according to the invention may includecalculation means 470 adapted to, preferably configured to, implement acomputer program configured to perform:

-   -   A step of obtaining a measured value of at least one        physicochemical property of the excavated clay soil; and    -   A step of determining a deflocculating agent quantity and an        activating agent quantity suitable for the excavated clay soil        based on a comparison of the one or more measured values with        reference values.

Furthermore, the system according to the invention includes a controlmodule 480 configured to generate output signals for use by theautomated transport means. Such output signals will allow the system totransport the determined deflocculating agent and activating agentquantities to the mixing device 450. In addition, they may allow apredetermined excavated clay soil quantity to be transported to themixing device 450.

Preferably, the system for preparing a construction material accordingto the invention may further include: a screen, preferably a compactone, a soil crusher, a planetary mixer.

More preferably, it can include a soil crusher. In particular, the soilcrusher makes it possible to eliminate the presence of agglomerates thatcould influence the quality of the construction binder or the siteconcrete. In addition, the powdered clay soil will provide a homogeneousappearance in the site concrete.

Even more preferably, the system for preparing a construction materialaccording to the invention includes a sifter for isolating pebbles witha diameter greater than 10 cm, preferably greater than 2 cm. The systemfor preparing a construction material may also include a sorting means,for example of the sieve type, for isolating particles with a diameterof less than 50 μm, preferably particles with a diameter of less than 20μm. Advantageously, but not limitatively, the elements or particles thusseparated, such as for example sand and/or aggregate fractions, can bereused in the formulation of the construction material and in particularof the site concrete.

Alternatively, the excavated clay soil may not be pretreated, and all ofthe clay soil is used to obtain the construction material. In this case,the method allows a site concrete to be produced.

In addition, it may include a pollution-control device for treating theexcavated soil before it is used.

Thus, according to another aspect, the invention relates to aconstruction material formed from an excavated clay soil. In particular,this construction material may be prepared according to a preparationmethod according to the invention described above. For example, thisconstruction material is directly prepared according to a preparationmethod according to the invention described above.

The construction material according to the present invention ischaracterized in that it includes a deflocculating agent and anexcavated clay soil. It should be noted that the preparation of theconstruction material includes adding an activating agent. However,since this activating agent can react with the excavated clay soil, itis not systematically found in the construction material. Nevertheless,occasionally, the construction material according to the presentinvention may include a deflocculating agent, an activating agent, andan excavated clay soil.

Given the possible addition of fillers, the invention also relates to asite concrete characterized in that it includes a deflocculating agentand an excavated clay soil.

Alternatively, in the absence of added fillers, the invention alsorelates to a construction binder characterized in that it includes adeflocculating agent and an excavated clay soil.

Advantageously, the construction material according to the inventionincludes a mixture of different types of clays. In particular, it mayinclude a clay combination selected from:

-   -   illite and kaolinite,    -   illite and kaolinite and bentonite,    -   illite and bentonite,    -   kaolinite and bentonite,    -   illite and montmorillonite, or    -   a combination of kaolinite, illite, smectite, bentonite,        chlorite, montmorillonite, muscovite, hallocyte, sepiolite,        attapulgite, and vermiculite.

Furthermore, advantageously, the construction material is formed from anexcavated clay soil characterized in that it includes at most 80 wt % ofparticles larger than 2 μm, preferably at most 60 wt % of particleslarger than 2 μm. The content of particles larger than 2 μm can forexample be measured according to the NF X31-107 standard. Thus, theexcavated soil has preferably undergone a pretreatment step resulting ina particle size centered on a fraction with a size diameter less than orequal to 50 μm, preferably less than or equal to 20 μm.

Preferably, a construction material according to the invention comprisesat least 50 wt % of excavated clay soil, at least 60 wt % of excavatedclay soil, at least 70 wt % of excavated clay soil, at least 80 wt % ofexcavated clay soil, most preferably at least 90 wt % of excavated claysoil. This is advantageously the case when the construction material isa construction binder.

Indeed, selecting the deflocculating agent and activating agent quantityoffers the advantage of being able to form a construction binder with ahigh quantity of excavated clay soil without altering the mechanicalproperties of the resulting construction materials. When theconstruction material is a site concrete, it may include at least 10 wt% of excavated clay soil, at least 15 wt % of excavated clay soil, atleast 20 wt % of excavated clay soil, at least 30 wt % of excavated claysoil, at least 40 wt % of excavated clay soil, at least 50 wt % ofexcavated clay soil.

The deflocculating agent may account for at least 0.1 wt % of theconstruction material, at least 0.20 wt % of the construction material,at least 0.25 wt % of the construction material, preferably at least 0.5wt % of the construction material, more preferably at least 1 wt % ofthe construction material, even more preferably at least 1.5 wt % of theconstruction material, and for example at least 2 wt % of theconstruction material. This is advantageously the case when theconstruction material is site concrete.

The deflocculating agent may account for at least 0.30 wt % of theconstruction material, at least 0.5 wt % of the construction material,preferably at least 1 wt % of the construction material, more preferablyat least 1.5 wt % of the construction material, even more preferably atleast 2 wt % of the construction material, and for example at least 2.5wt % of the construction material. This is advantageously the case whenthe construction material is a construction binder.

In addition, the deflocculating agent may account for at most 20 wt % ofthe construction material, preferably at most 15 wt % of theconstruction material, and more preferably at most 10 wt % of theconstruction material.

In particular, the deflocculating agent may account for between 0.25 and10 wt % of the construction material, preferably between 0.5 and 10 wt %of the construction material, more preferably between 1 and 10 wt % ofthe construction material, even more preferably between 2 and 8 wt % ofthe construction binder, and for example between 2 and 5 wt % of theconstruction binder. Thus, the deflocculating agent may preferablyaccount for between 0.1 and 5 wt % of the construction material.

In particular, the deflocculating agent accounts for at least 0.5 wt %of the excavated clay soil, preferably at least 1 wt % of the excavatedclay soil, more preferably at least 2 wt % of the excavated clay soil,even more preferably at least 3 wt % of the excavated clay soil, and forexample at least 4 wt % of the excavated clay soil. Indeed, with suchdeflocculating agent concentrations, the binder formulation according tothe invention can then be used in combination with an activatingcomposition to form a material with advantageous mechanical properties.

Furthermore, the deflocculating agent accounts for at most 20 wt % ofthe excavated clay soil, preferably at most 10 wt % of the excavatedclay soil. Indeed, too high a concentration is not necessary to form amaterial with advantageous mechanical properties.

In particular, the deflocculating agent accounts for between 0.5 and 20wt % of the excavated clay soil, preferably between 1 and 10 wt % of theexcavated clay soil, more preferably between 3 and 10 wt % of theexcavated clay soil and even more preferably between 4 and 10 wt % ofthe excavated clay soil.

The activating agent is, for example, present at a content of at least 5wt % of the construction material, preferably at least 7 wt % of theconstruction material, more preferably at least 8 wt % of theconstruction material. This is advantageously the case when theconstruction material is a site concrete.

The activating agent may be present at a content of at least 10 wt % ofthe construction material, preferably at least 15 wt % of theconstruction material, more preferably at least 20 wt % of theconstruction material, even more preferably at least 25 wt % of theconstruction binder, and for example at least 30 wt % of theconstruction binder.

In addition, the activating agent may account for at most 50 wt % of theconstruction material, preferably at most 45 wt % of the constructionmaterial, and more preferably at most 40 wt % of the constructionmaterial. This is advantageously the case when the construction materialis a construction binder.

The activating agent may also account for at most 15 wt % of theconstruction material, preferably at most 12 wt % of the constructionmaterial, and more preferably at most 10 wt % of the constructionmaterial. This is advantageously the case when the construction materialis a site concrete.

In particular, the activating agent may account for between 3 and 12 wt% of the construction material, preferably between 4 and 10 wt % of theconstruction material, more preferably between 5 and 10 wt % of theconstruction material. This is advantageously the case when theconstruction material is a site concrete.

In particular, the activating agent may account for between 10 and 80 wt% of the construction material, preferably between 15 and 80 wt % of theconstruction material, more preferably between 20 and 80 wt % of theconstruction material, even more preferably between 30 and 80 wt % ofthe construction material, and for example between 40 and 60 wt % of theconstruction material. This is advantageously the case when theconstruction material is a construction binder.

In one particular embodiment, a construction material, preferably aconstruction binder according to the invention comprises:

-   -   30% to 80 wt % of an excavated clay soil,    -   1% to 10 wt % of a deflocculating agent, and    -   10% to 50 wt % of an activating agent.

Preferably, a construction material, preferably a construction binder,according to the invention comprises:

-   -   50% to 75 wt % of an excavated clay soil,    -   1% to 10 wt % of a deflocculating agent, and    -   15% to 50 wt % of an activating agent.

More preferably, a construction material, preferably a constructionbinder according to the invention comprises:

-   -   50% to 70 wt % of an excavated clay soil,    -   2% to 5 wt % of a deflocculating agent, and    -   15% to 45 wt % of an activating agent.

More preferably, a construction material, preferably a constructionbinder, according to the invention comprises:

-   -   50% to 60 wt % of an excavated clay soil,    -   2% to 5 wt % of a deflocculating agent, and    -   25% to 45 wt % of metal oxides.

Even more preferably, a construction material, preferably a constructionbinder, according to the invention comprises:

-   -   30% to 80 wt % of an excavated clay soil,    -   1% to 10 wt % of a deflocculating agent,    -   10% to 40 wt % of metal oxides, and    -   2% to 15 wt % of a strong base.

Even more preferably, a construction material, preferably a constructionbinder, according to the invention comprises:

-   -   30% to 80 wt % of an excavated clay soil,    -   0.1% to 10 wt % of a deflocculating agent, and    -   15% to 50 wt % of blast furnace slag.

Even more preferably, a construction material, preferably a constructionbinder according to the invention comprises:

-   -   30% to 80 wt % of an excavated clay soil,    -   0.1% to 10 wt % of a deflocculating agent,    -   10% to 45 wt % of blast furnace slag, and    -   5% to 20 wt % of an alkaline composition such as triphosphate.

Preferably, a construction material according to the invention is a siteconcrete comprising:

-   -   between 5 and 45 wt %, preferably between 5 and 30 wt %, more        preferably between 10 and 20 wt % of a construction binder        according to the invention;    -   between 25 and 45 wt %, preferably between 30 and 40 wt % of        sand, for example from site soil, preferably from excavated clay        soil;    -   between 35 and 55 wt %, preferably between 40 and 50 wt % of        aggregates, for example from site soil, preferably from        excavated clay soil; and    -   preferably between 2 and 10 wt % of water.

More preferably, a construction material according to the invention is asite concrete comprising:

-   -   between 5 and 20 wt % of raw clay from the excavated clay soil,        preferably between 5 and 15 wt % of raw clay from the excavated        clay soil;    -   between 0.1 and 3 wt % of a deflocculating agent;    -   between 3 and 15 wt %, preferably between 5 and 12 wt % of an        activating agent; for example, between 5% and 10 wt % of a blast        furnace slag;    -   between 25 and 45 wt %, preferably between 30 and 40 wt % of        sand, for example from site soil, preferably from excavated clay        soil;    -   between 35 and 55 wt %, preferably between 40 and 50 wt % of        aggregates, for example from site soil, preferably from        excavated clay soil; and    -   preferably between 2 and 10 wt % of water.

Sand and aggregates may be obtained from quarries. In addition, thebinder may include quarry clay to supplement the clay from the excavatedclay soil.

In addition, the site concrete may include admixtures such asplasticizers, superplasticizers, rheological retention agents, orair-entraining agents.

In addition, the water to dry matter weight ratio of the constructionbinder is advantageously controlled and is preferably less than 1, morepreferably substantially equal to 0.6.

In addition, according to another aspect, the invention relates to aconstruction material formed from a construction binder according to theinvention.

Furthermore, the invention relates to a construction material obtainedfrom a preparation method according to the invention. The inventionrelates to a construction material obtained from a preparation methodaccording to the invention.

The invention allows in particular the production of:

-   -   insulating construction material: from a construction binder        according to the invention with the addition of light aggregates        of the “vegetable or porous” type;    -   lightweight concrete: from a construction binder according to        the invention with an added foaming agent of the aluminum powder        type. This will trap air in the material and improve its        insulating properties;    -   Prefabrication elements: manufacture of concrete blocks or slabs        in a factory from the construction binder according to the        invention; and    -   Isolation modules.

As illustrated by the following examples, the present invention providesa solution based on a mixture of a raw clay matrix, a deflocculatingagent, and an activating composition to provide a construction materialwith mechanical properties similar to the standard while having areduced carbon footprint.

EXAMPLES

Methodology for Measuring the Physicochemical Properties of the ClaySoil:

The clay soil is pre-sieved to remove all elements or particles with adiameter greater than 20 μm. Such a pretreated clay soil is particularlysuitable for forming a construction binder according to the invention.

The pH is measured using 20 g of pretreated clay soil mixed with 100 mLof distilled water. After stirring for 20 minutes at 150 rpm (for“revolutions per minute” according to an Anglo-Saxon terminology), thesuspension is filtered and then the pH of the filtered solution ismeasured.

The clay content is measured in a conventional way by the granulometricmethod described in the NF X31-107 standard.

The nature of the clays is conventionally measured by X-raydiffractometry.

Generation of Similarity Values

As presented previously, the values include correlations betweenmeasured values of at least one physicochemical property of a clay soiland deflocculating agent and activating agent quantity values.

These reference values are generated from a plurality of clay soilsamples coupled with varying deflocculating agent and activating agentquantities in a method for preparing a construction binder describedbelow.

The generation of reference values may for example implement anexperimental design such as a simplex design, a screening design, afactorial design, a response surface design, a mixture design, a Taguchidesign.

Table 1 below presents the physicochemical properties of differentexcavated soil samples while Table 2 shows an example of an experimentaldesign to generate reference values.

TABLE 1 Physicochemical properties Clay soil pH Clay content Nature ofthe clays Sample A 7 to 8 90% à 100% Smectite and MontmorillioniteSample B 4 to 6 90% à 100% Kaolinite

TABLE 2 Deflocculating agent Activating agent Clay Concen- Concen-Reference soil Nature tration Nature tration MUP42 Sample na 0 wt %LHF + 23 wt % A of the Alkaline of the binder solution binder MUP5BSample na 0 wt % LHF + 43 wt % A of the Triphosphate of the binderbinder MUP12 Sample na 0 wt % Blast furnace 25 wt % A of the slag of thebinder binder MUP11 Sample Sodium 2.73 wt % Blast furnace 25 wt % Ahumates of the slag of the binder binder MUP2 Sample Sodium 2.96 wt %Metal oxides 12 wt % A humates of the of the binder binder MUP5 SampleSodium 3.13 wt % LHF + 42 wt % A humates of the Triphosphate of thebinder binder MUP41 Sample Sodium 3.39 wt % LHF + 22 wt % A humates ofthe Alkaline of the binder solution binder MUP3 Sample Sodium 3.97 wt %Metal oxides 9 wt % A humates of the of the binder binder

Preparation of a Construction Binder:

The construction binders, in particular when generating the referencevalues, are prepared according to an identical protocol, i.e. a premixis made between a clay soil and a deflocculating agent in thepredetermined quantities according to, for example, an experimentalplan, and then water is added and the suspension is mixed at low speed,that is to say substantially at six hundred revolutions per minute forthirty seconds. Next, an activating agent is added to the premix andthen the premix is mixed at high speed, that is to say at about fifteenhundred revolutions per minute for three minutes.

The weight ratio of water to dry matter of the composition (also calledthe construction binder) is adjusted to a value lower than 1, morepreferably substantially equal to 0.6.

The thus-formed construction binder is then poured into a mold and leftto cure at room temperature, that is to say around 20 degrees Celsius,for 28 days.

The mechanical properties of the construction binder are then evaluated.

Methodology for Measuring the Mechanical Properties of ConstructionBinders:

After curing is completed, the construction binder is removed from themold and the mechanical strength is measured. By mechanical strength ofa construction binder is meant its compressive strength, suchcompression being measured in accordance with the NF EN 196-1 standard.

The results of the measurements performed on the experiments describedin Table 2 are presented below in Table 3.

TABLE 3 Mechanical strength Reference (in MPa) MUP42 27 (comparativeexample) MUP5B 25 (comparative example) MUP12 21 (comparative example)MUP11 41 MUP2 37 MUP5 45 MUP41 43 MUP3 37

These results show that depending on the activating agent anddeflocculating agent quantities used, the performance of the binderformed will be different and in particular its mechanical strength.

In addition, they show that the presence of a deflocculating agentallows mechanical strengths higher than 30 MPa to be obtained.

Selection of the Composition of a Construction Binder:

After the preparation of reference values and, if necessary, acalculation algorithm, it is possible to implement a method forselecting the appropriate deflocculating and activating agent quantitiesfor a given excavated clay soil.

First, a sample of the excavated clay soil is sieved so as to remove allelements or particles with a diameter greater than 20 μm.

The physicochemical properties of the pretreated excavated clay sampleare then analyzed as described above.

The values obtained are then transmitted to a computer device configuredto implement the method according to the invention.

The latter then generates values for the deflocculating agent andactivation agent quantity that will, when coupled with a predeterminedquantity of excavated soil, form a construction binder.

Formation of a Construction Binder According to the Invention

The excavated clay soil is then sieved to remove any elements orparticles larger than 2 cm in diameter and then a predetermined quantityof a pretreated excavated clay soil is mixed simultaneously orsequentially with the selected deflocculating agent and activationquantity values.

The construction binders or site concretes formed according to theinvention have compressive strengths equivalent to the compressivestrengths obtained with a concrete formed with Portland cement. Thus,the present invention allows the appropriate composition to be selected,which will make it possible to form a low-carbon construction binder,from excavated clay soil, having sufficient mechanical properties tomake it a construction material meeting the majority of the needs of thesector.

The invention claimed is:
 1. A construction material comprising anexcavated raw clay soil and a deflocculating agent, said excavated rawclay soil comprising a mixture of different types of clays including oneof the following mixtures: illite and kaolinite, illite and kaoliniteand bentonite, illite and bentonite, kaolinite and bentonite, illite andmontmorillonite, or kaolinite, illite, smectite, bentonite, chlorite,montmorillonite, muscovite, hallocyte, sepiolite, attapulgite, andvermiculite.
 2. The construction material according to claim 1, whereinthe excavated raw clay soil has not undergone a combustion stage.
 3. Theconstruction material according to claim 1, further comprising analkaline activating agent.
 4. The construction material according toclaim 3, said alkaline activating agent being a composition including acompound having a pKa greater than or equal to
 10. 5. The constructionmaterial according to claim 3, comprising: 30 to 80 wt % of theexcavated raw clay soil, 1 to 10 wt % of the deflocculating agent, and10 to 50 wt % of the alkaline activating agent.
 6. The constructionmaterial according to claim 1, said construction material comprising atleast 0.1 wt. % of said deflocculating agent.
 7. The constructionmaterial according to claim 1, said construction material comprising atleast 2 wt. % metal oxides.
 8. The construction material according toclaim 7, said construction material having a water to dry matter weightratio less than
 1. 9. The construction material according to claim 1,said excavated raw clay soil having particles of a size greater than 50μm.
 10. The construction material according to claim 1, saiddeflocculating agent is selected among a nonionic surfactant, an anionicsurfactant, a polyacrylate or an amine.
 11. The construction materialaccording to claim 1, further comprising blast furnace slag.
 12. Theconstruction material according to claim 11, comprising: 30 to 80 wt %of the excavated raw clay soil, 0.1 to 10 wt % of the deflocculatingagent, and 5 to 10 wt % of the blast furnace slag.
 13. The constructionmaterial according to claim 1, said construction material being aconstruction binder.
 14. The construction material according to claim 1,said construction material being a site concrete.
 15. The constructionmaterial according to claim 14, comprising: 5 to 20 wt % of theexcavated raw clay soil; 0.1 to 3 wt % of the deflocculating agent; 3 to15 wt % of an activating agent; 25 to 45 wt % sand; and 35 to 55 wt %aggregates.
 16. The construction material according to claim 14, saidsite concrete including at least one of the following: plasticizers,superplasticizers, rheological retention agents or air-entrainingagents.
 17. The construction material according to claim 1, furthercomprising at least 2 wt % silt particles.
 18. The construction materialaccording to claim 1, the excavated raw clay soil having 80 wt % or lessof particles larger than 2 μm.